Roast vegetables have always had that warm glow of health. Every cook from Jamie Oliver to your gran tells you they are good for you.

But they could actually be as bad for your teeth as fizzy drinks, scientists have claimed.

Roasting vegetables increases their acidity, research has found. Food acids are a major cause of dental erosion.

The worst culprits are said to be green peppers, courgettes and aubergines.

Stewing the vegetables was better for teeth, researchers at Dundee University’s School of Dentistry concluded.

Dr Graham Chadwick said: ‘If you roast many vegetables, it will increase their acidity. It is the same with ratatouille, which is a very popular vegetarian dish. When it is ovenroasted, its acidity is the same as that of some carbonated drinks.

‘Professional chefs know this already, because the acid is what makes the dishes taste better. In fact, if I was cooking ratatouille, I would roast it as well, because it tastes better that way.

‘Vegetables obviously have their health benefits, reducing obesity and cancer risks, but it’s great there is interest in this because people will start thinking more carefully about how what they eat affects their teeth.’

Vegetables were tested after being roasted and stewed by being covered in an alkaline fluid. The more fluid that was needed to create a neutral pH reading, the more acidic they had become.

The variation in results was put down to the fact that acids are diluted by the comparatively large amounts of liquids used as stock in stews.

The research was published in the European Journal of Prosthodontics and Restorative Dentistry.